Filtration systems having particulate filter media are used to purify water and other contaminated fluids of particulate contaminates and organic contaminates. The design of the basic filtration system is relatively simple, however, the problem of how to periodically regenerate a particulate filter medium has complicated the filtration apparatus.
The most common solution to the problem has been to backwash the filter medium, that is, reverse the direction of flow through the filter medium. Backwashing is subject to at least two major shortcomings. First, the particulate filter medium traps contaminates that require much more energy to remove from the filter medium than the energy required to trap the contaminates in the first place. Therefore, reversing the flow through the filter medium cannot dislodge such contaminates. After a short time, the filter medium begins to form into balls of tar and to have vertical channels. Secondly, the particulate filter medium is resettled by gravity. The particulate filter medium tends to resettle non-uniformly and in strata: the heavier particles tend to settle toward the bottom and the lighter particles tend to settle toward the top. When the particulate filter medium is stratified or has vertical channels, the effectiveness of the filter medium is greatly impaired.
Another solution to the problem of regenerating the particulate filter medium has been to remove the particulate filter medium from the filtration vessel and scrub it in a separate vessel. This solution is also subject to at least one major shortcoming. The process of removing the filter material from the filtration vessel, cleaning the filter medium, and returning the filter medium to the vessel is extremely complicated and presents difficult engineering problems.
But one of the most persistent problems with backwashing or scrubbing the particulate filter medium has been collapsing of the backwash screen. A screen is used to retain the particulate filter medium within the filtration vessel during filtration and backwash cycles. The backwash screen is typically formed into a cylindrical shape. During a backwash cycle, the high velocity of the particulate filter medium within the filtration vessel and the high pressure drop across the screen causes the filter medium to be driven into the screen with such velocity that the screen becomes plugged and collapses. Even if the screen does not collapse, the screen becomes partially plugged and begins to act as a filter preventing contaminates from exiting the filtration vessel during a backwashing or scrubbing cycle.
Therefore, it is an object of the present invention to provide a filter system having a particulate filter medium that can be thoroughly scrubbed of accumulated contaminates, including contaminating particulates and contaminating oils, greases, and waxes. It is a further object of the invention to provide a scrubbing apparatus and method that scrubs the particulate filter medium within the filtration vessel. It is an important object of the invention to provide a scrubbing apparatus that will not plug or collapse the screens used to retain the filter medium within the filtration vessel. It is another object of the invention to provide a simple, low maintenance filtration system and method. It is another object of the invention to provide an apparatus and method to force settle a particulate filer medium so that the filter medium is randomly and uniformly reconstituted. Further objects and features of the invention will be apparent to those skilled in the art upon reading the following detailed disclosure.